From the Custom Maps Troubleshooting :
Animal population is very low, animals seem bugged, get stuck a lot, walk over/under water and tracking is impossible.
Extreme animal-related problems are caused by a broken NavMesh. It happens when steps of the initial server startup instructions were omitted or weren't done correctly. You can force the server to recreate a new, clean NavMesh file based on your terrain at any time. Therefore:
- Shut down the server.
- Delete the /dava/NavMeshes/nm1.nmesh file from your LiF:YO server directory.
- Delete the folder that relates to your World ID from the /data/NavMeshes/cached/ path of your LiF:YO server directory.
- Start your server. It'll create a new NavMesh on startup. Will take a few minutes.
Furthermore, please take into account that most custom maps are much larger than the original map. If you don't increase server animal count, overall density will be lower naturally due to the higher amount of landmass available.
Source : https://feudal.tools/index.php?s=faq